powder increments for velocity testing?

S

Shadow9mm

New member
I am preparing to do some velocity ladder testing (i think that is what its called) for my 308. I worked up to max with no pressure signs. I am planning to work back down from max to get a nice consistent and stable velocity window.

When working up to max I usually go in increments of roughly 1% of max. so for 223 about 0.2g increments. for 308 and 30-06 usually 0.5g increments.

For testing for velocity, working back down to find a good stable spot I am somewhat unsure. I have been trying to improving my processes and am trying to have a reason behind them. I was debating on 0.2g or 0.3g increments. 0.1g increments seem too small and I don't know that I can consistently measure that accurately anyway. 0.2 is similar problem. I am concerned that 0.3g or 0.4g increments might be too coarse. to give me that data I need. I am just not sure how to proceed.

Keep in mind I am using a basic balance bean scale. And while I am trying to make some nice target ammo, its going in a hunting gun not a target rifle. Just trying to follow all the steps and not take short cuts to make the best ammo I am able to at this point.

Mossberg Patriot in 308
BL-c(2) powder, Max 0f 47.0g
CCI Large Magnum Rifle primers
LC16 brass (I tested up to max, no pressure signs)
Hornady 168g OTM bullets
Bullet jump of 0.065 at max max length COL.
 
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It's probably better to weigh powder than beans. The gas resulting from the latter doesn't contain its own oxygen for combustion, so you will have to find a practical way to introduce oxygen to get enough combustion energy out of it to move a bullet. It will probably require very low temperatures so you can use both gas and oxygen in the liquid state. :D

I think Dan Newberry's rule of thumb to use 0.7% to 1.0% of the maximum load for each load increment is pretty reasonable. I favor the lower end of that range as I've had 0.5-grain loads skip past a good load point in one particular .308 Win load with a maximum of about 46 grains. If you have a 30-06 load maximum of 60 grains, then 0.5-grains should be fine.
 
so keep it at or under 1% of max or you could miss data points.
For this load with a max of 47g
1% would be .47g
0.7% would be 0.39g

sine I an used to fine tuning with 0.2g increments I'm a little shy of jumping straight to 0.4g jumps. I will use 0.3g jumps this go around. but it gives me a lot more range.
 
You may want to pick up a copy of the latest Hornady Handbook of Cartridge Reloading, whatever the latest edition is , (mine is #8 but I believe #9 is out and maybe #10 soon) instead of listing a minimum charge and a maximum charge with a powder ... they list what powder charge will give you different velocities . Like this : 308 Win / 150 gr. bullets
VARGET POWDER -
2300 fps - 35.9 grs.(start)
2400 fps - 38.2 grs.
2500 fps - 40.4 grs.
2600 fps - 42.6 grs.
2700 fps - 44.9 grs. (max)

I find this approach very useful when working up loads . You can see how many grains will move your velocity up or down 100 feet per second .
And To me this is more information than simply a min and max load .
My first reloading manual Hornady Manual edition #1 1967 was set up this way and helped me work up loads .
Let's say I want my 150 gr. bullet to have a velocity of 2650 fps ... I would start with 43.7 grs. of Varget ( 42.6 + 44.9 = 87.5 /2 = 43.75)
I would then try 0.50 grs above and below that charge ...
...43.2 grs - 43.7 grs. - 44.2 grs ... test these loads and see how they work out .
Next I might fine tune the charge with 0.25 grain adjustments ...
Usualy in rifles 0.50 gr. adjustments get you where you want to be especially if you are close to your velocity goal to start with .
Gary
 
gwpercle said:
You may want to pick up a copy of the latest Hornady Handbook of Cartridge Reloading, whatever the latest edition is , (mine is #8 but I believe #9 is out and maybe #10 soon) instead of listing a minimum charge and a maximum charge with a powder ... they list what powder charge will give you different velocities . Like this : 308 Win / 150 gr. bullets
VARGET POWDER -
2300 fps - 35.9 grs.(start)
2400 fps - 38.2 grs.
2500 fps - 40.4 grs.
2600 fps - 42.6 grs.
2700 fps - 44.9 grs. (max)

I find this approach very useful when working up loads . You can see how many grains will move your velocity up or down 100 feet per second .
And To me this is more information than simply a min and max load .
My first reloading manual Hornady Manual edition #1 1967 was set up this way and helped me work up loads .
Let's say I want my 150 gr. bullet to have a velocity of 2650 fps ... I would start with 43.7 grs. of Varget ( 42.6 + 44.9 = 87.5 /2 = 43.75)
I would then try 0.50 grs above and below that charge ...
...43.2 grs - 43.7 grs. - 44.2 grs ... test these loads and see how they work out .
Next I might fine tune the charge with 0.25 grain adjustments ...
Usualy in rifles 0.50 gr. adjustments get you where you want to be especially if you are close to your velocity goal to start with .
Gary
Click to expand...
I have a hornady manual with that format as well. Never thought about it in that aspect. With that said my loads never seem to match the manual. They are generally lower, on rare occasions higher. In this case hogdon shows 2754 at 47.0g out of a 24in barrel. I am getting 2783 at 46.2g out of a 22in barrel. I'm chalking it up to the long jump of 0.065 at max mag length. Unfortunately hornady doesn't list bl-c(2).
 
If you plan to later fine tune in .2gr increments . Id go with the .4 increments so you just splitting that in half to fine tune . I’ll say this though , if you need to tweek something buy .2gr to get it to shoot better . You are not in the sweet forgiving powder charge spot .

For 223 I do .3 increments and 308 .4 FWIW . Like you ( maybe ) I don’t have a scale that can do .2gr increments consistently even with check weights so I don’t bother going below .3gr
 
This is one of those personal preference answers:

When getting in the ballpark, I use the 1% jumps in max powder charge rounded down. So a 47.0g max charge = 0.4 g jumps when getting to the pall park.
When fine tuning I find the nodes and split the difference in the node, so 45.5 and 46.4 is my node I go to around 46.0 and test, then work half up and down, 0.2 charge more and less then the 46.0 and test. Now this is more round usage then some people like, but then again we are talking fine tuning. Most of the time a node is pretty accurate for 90% of use so going to the low end of the node for powder conservation is my norm.

Short answer: 0.4 g increments for 308 is fairly well used by alot of folks and will get you where you need to be.
 
Note that Hornady and Sierra and others using the velocity column layout generally get those numbers with a particular production gun and list several bullets of similar (sometimes not always exact) weights together, so you can expect some variation by bullet shape, especially if your throat geometry doesn't match the one they had exactly. Obviously, your barrel length has to match, too.
 
Note that Hornady and Sierra and others using the velocity column layout generally get those numbers with a particular production gun and list several bullets of similar (sometimes not always exact) weights together, so you can expect some variation by bullet shape, especially if your throat geometry doesn't match the one they had exactly. Obviously, your barrel length has to match, too.
Click to expand...

I have my own theory on this aspect of Hornady's manual . I "believe" ( no evidence ) that Hornady "in general" takes the heaviest and longest baring surface bullet on each page and that's the bullet the data/charge is actually for on that page .

My thinking is that's why so many say Hornady's data is a little on the weak side . They have data using 180gr .308 bullet with VERY long baring surfaces lumped in with the 178gr match bullets with the long ogives and boat tails leaving a very short baring surface . Lighter bullet with less drag in the bore means ????

Beger makes heavy for caliber/cartridge bullets with very short baring surfaces . They claim it's to help push those heavy bullets faster do to the low drag down the bore .

Here is an example of this . The center bullet is a Berger 200gr .308 bullet . Note the barring surface is the same or less then all the other lighter bullets around it .

175gr TMK , 195gr ELD , 200gr Berger , 190gr SMK , 175gr SMK
pPNXVI.jpg
 
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That makes sense. I always found it odd that they used the same loads for so many bullets. But if they take the heaviest bullet with the longest bearing surface everything under that is safe.

With that said, as you noted, the data is only going to be accurate for that bullet, and the rest is going to be off a bit.
 
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